Techniques for integrating MEMS devices and circuit chips are important especially for the application of MEMS array-type devices. Through these techniques it is possible to integrate MEMS units of the MEMS array-type devices such as capacitive micromachined ultrasonic transducer (CMUT) and reflective micromirror array and circuit chips, thereby achieving the most effective electrical connections and control. For example, the optical array-type devices commonly adopted for many fields comprise a plurality of reflective micromirrors. These reflective micromirrors may rotate about a fixed axis to guide light toward an emitting direction. Please refer to FIG. 1. FIG. 1 illustrates a structure of the optical array-type device disclosed by U.S. Pat. No. 5,083,857. This optical array-type device 10 comprises a reflective mirror 11 and a flexible structure 15. The reflective mirror 11 is firmly connected to the flexible structure 15 via a anchor structure 12. Furthermore, the optical array-type device 10 also comprises an electrode 14. The electrode and the flexible structure 15 jointly form an actuator unit. It is possible to control the deformation of the flexible structure 15 hence the inclination angle of the reflective mirror 11 (see dashed lines 11a and 11b in FIG. 1) through inputting a control signal to the electrode 14. By adjusting the inclination angle of the reflective mirror 11, it is possible to adjust the light emitting direction in order to generate the expected optical effect. Since more planar the surface of the reflective mirror 11 is the bigger the effective area lit by the incident light is, the flexible structure 15 is designed to be hidden under the reflective mirror 11. This would better the device performance, but also make the manufacturing process more challenging. Moreover, it is noted from FIG. 1 that a recess 13 is formed right in the center of the reflective mirror 11. The recess 13 rises from a process of manufacturing the anchor structure 12 and it would prevent the light passing therethrough from being reflected effectively, thereby reducing device performance. In the process for manufacturing the optical array-type device 10, the reflective mirror 11 is formed by performing micromachining processes on a circuit wafer (please refer to FIGS. 7a-7b in U.S. Pat. No. 5,083,857 for detailed manufacturing processes). In order to avoid adversely affecting the circuitry on/in the circuit wafer, process temperatures and materials used to manufacture the optical array-type device should be limited to low temperature formed materials such as metals. However, this limitation would degrade structural reliability, surface roughness and surface topography hence total quality of the finished optical array-type device 10.